Active gauge protection for drill bits

ABSTRACT

A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, the drill bit comprising a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter; and a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.

FIELD OF INVENTION

The present invention relates in general to drill bits and, more specifically, to protecting the drill bit and casing from damage during tripping in and drill out operations.

BACKGROUND OF INVENTION

A variety of drill bits, including fixed and rotary bits, are used in drilling operations. One part of the drilling operation that occurs before penetration into a formation involves drilling through a concrete pad at the bottom of a borehole called the “shoe”. This operation is called “drill out”, wherein the cement is “tagged up” as the drill bit drills through the structure. Often this pad is formed from the residue of casing operations of the borehole but it may also form from intentional filling the bottom of the borehole with cement. The shoe functions to cap the formation at the bottom of the metal casing until the drilling operator wishes to drill into the formation below the shoe.

One significant problem that may occur during drill out is that the drill bit, upon initial contact with the shoe, may begin to move off-center from the center of the borehole. The drill bit may become temporarily destabilized and begin angling where it cuts a wider diameter hole than the planned hole diameter, called the “gauge diameter”. The drill bit may also begin “whirling”—a complex set of repeating rotational motions that also cause the bit to go off-center. Under such conditions, an unprotected drill bit may continue to spin outside its designed gauge diameter and eventually come into contact with the casing, severely damaging the cutting elements of the drill bit.

A drill bit spinning at normal operational speed may contact the borehole wall with tremendous force. This contact may cause several events to occur. For example, the drill bit may remain unstable and possibly build up more instability, causing it to wander off the intended drill path or drill at awkward angles. The drill bit, because of the rotational force it operates under, may ricochet off the side of the borehole and bounce towards the opposing sidewall. The cutters, especially the gauge cutters, may become directly exposed to the casing wall and impact the casing, leading to chipped, cracked, or complete destruction of the face of the cutting element, which may fail under a sudden shock impact. The casing wall itself may become scarred or gouged by the impact of the cutters, which are typically made of a very hard material that can cut through metal (such as polycrystalline diamond compact).

Accordingly, it is desirable to provide an apparatus that avoids the aforementioned limitations and allows for protection of the drilling components and casing interior during tripping in the hole and during the drill out process.

SUMMARY OF INVENTION

Apparatus and methods are disclosed to protect for the cutting elements, specifically the gauge cutters, from coming into contact with the borehole casing during both traversal down the hole and during drill out operations. For example, dynamic forces, including “whirl”, may cause the drill bit to either rotate off-center in the borehole or rotate in a diameter beyond the gauge diameter of the bit. The protective inserts of the present invention may prevent the cutting elements of the bit from coming into contact with the borehole casing by acting as a first point of impact for the bit, to minimize damage to the gauge cutters. The protective inserts may also minimize gouging of the casing wall by acting as a smooth bearing surface during bit rotation. The protective inserts of the present invention may act as an additional gauge after abrasion wears the invention down to gauge diameter.

A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, is disclosed. The drill bit includes a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter, and a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.

A method of protecting a gauge cutter of a drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, is disclosed. The method includes the steps of coupling a protective insert to the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, positioning the drill bit within the casing, and preventing the gauge cutter from contacting the casing inner wall along a selected length of the casing.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing summary as well as the following detailed description of illustrative embodiments of the invention will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown herein. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

The invention may take physical form in certain parts and arrangement of parts. For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a perspective view of an example of a drill bit having the presently disclosed protective inserts;

FIG. 1B is a bottom view of the face of the drill shown in FIG. 1A; and

FIG. 2 is a view of an embodiment of a drill bit of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.

As used herein, the terms “up” and “down”; “upper” and “lower”; “uphole” and “downhole” and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point.

An apparatus and method to protect the cutting elements of a drill bit, specifically the gauge cutters, from coming into contact with the borehole casing during both traversal down the hole and during drill out operations are disclosed. The drill bit comprises one or more protective inserts that protrude beyond the gauge distance and into the drift distance between the drill bit and inner wall of the casing. These exposed protective inserts prohibit the gauge cutters from engaging the casing wall. The protective inserts may also allow the drill bit to rotate within the casing without damaging the casing. Once the drill bit drills into the formation, the protective inserts may ablate to allow the gauge cutters to engage the formation. Accordingly, the present invention provides active gauge protection for the drill bit by providing a physical barrier between the cutters and the casing.

FIGS. 1A and 1B, show an example of a bit tool including an embodiment of the active gauge protection, shown generally at 10. Bit 10 may be any cutting or boring tool suitable for drilling into earth formations, and may be made from any suitable material. For example, bit 10 may be a drag bit. Bit 10 includes a body 12 having a curved or dome-like face 14 that extends from a vertical centerline 16 of body 12. During operation of bit 10, face 14 may be positioned towards the formation to be drilled. A threaded shank 18 may be provided on the opposing end of bit 10 to allow bit 10 to be coupled to a drill string and allow the drill string to control and bit 10.

Bit 10 includes one or more bit blades 20. Bit blades 20, may be positioned and spaced uniformly between one another, extend from an area beginning approximately about the centerline 16 and radiate outward towards the outer diameter of bit 10. As blades 20 reach the outer diameter of bit 10, the angle of blade 20 may become substantially parallel with centerline 16, e.g., an area on blade 20 substantially parallel to casing 50 and substantially perpendicular to the bottom of the borehole.

One or more super-abrasive cutters 22, made of materials such as polycrystalline diamond compact, matrix, diamond impregnation, or tungsten carbide, for example, are coupled to each blade 20. The cutting face 23 of each cutter 22 may face in the general direction of the operational rotation of bit 10. Each cutter 22, as bit 10 rotates during normal operation, may create cuttings by interacting in an abrasive manner with the concrete shoe 90 (shown in FIG. 2) and later the virgin rock formation below shoe 90. As cutters 22 cut shoe 90 and then the formation during normal operation, a fluid flow channel 30 may bring fluid through nozzles 32 onto face 14 of bit 10 to help wash the cuttings through channels 34 and away from cutters 22. Fluid flow from nozzles 32 may also act to cool the cutting faces 23 as they perform their abrasive action.

FIG. 2 shows a cross sectional view of bit 10 and blade 20. Gauge cutters 25 may be positioned relative to the outer diameter of bit 10 and uphole from cutters 22 on each blade 20. Gauge cutters 25 may be a series of cutters 22 shaped and sized to cut the formation in such a way as to create a borehole with the proper gauge diameter 62. Gauge cutters 25 may be the radially outermost cutters on blade 20 from centerline 16. As shown in this view, one or more gauge cutters 25 and cutters 22 may be positioned in an overlapping formation in view of the direction of rotation to ensure redundant coverage during drilling operations.

Referring to FIG. 2, drill bit 10 may be coupled to a drill string (not shown) and positioned into the borehole via borehole casing 50. During drillout and formation drilling, bit 10 may traverse down the borehole and begin drilling operations within the confines of a borehole casing 50. Casing 50 may be composed of steel or other suitable materials. The borehole may have a casing diameter 52, which may be defined as the diameter between opposing points in the substantially circular hole casing 50. Casing 50 may act as a brace against hole collapse and maintain a clear path for tools and resources to traverse to and from the operational point. At the bottom of casing 50 there may be a concrete “shoe” or plug 90 within the confines of casing 50. Shoe 90 may serve to seal off the formation from the open borehole above and may also include leftover material from prior casing operations that may have flowed to the bottom of the borehole. Shoe 90 may also contain other debris from prior operations, including glass, metal, electronics, and other materials that might have fallen or been placed prior into the borehole. For bit 10 to reach virgin formation through the borehole, bit 10 may need to drill through shoe 90 in an operation known as “drillout” or “tagging up” shoe 90.

To accomplish the drillout operation and initial penetration of the formation beneath shoe 90, bit 10 may be designed to have an operational diameter called a gauge diameter 62. Gauge diameter 62 may be diameter of the hole drilled by bit 10 and may represent the circular area effectively contacted by cutters 22. The space left between gauge diameter 62 and casing diameter 52 may be referred to as drift distance 72. Drift distance 72 on all sides of bit 10 may permit bit 10 to operate within casing 50 unencumbered and may also permits fluid and debris to flow uphole and away from cutting faces 23. Drift distance 72 may also allow for potential variations in casing diameter 52 due to inconsistent drilling, formation movement, or casing buckling while still allowing a tool with a certain gauge diameter 52 can pass through to the bottom of casing 50.

As shown in FIGS. 1A, 1B and FIG. 2, bit 10 includes one or more protective inserts 100. Protective inserts 100 are coupled or positioned on bit 10 to minimize or prevent contact between the cutting elements of bit 10 and the interior of casing 50. For example, protective insert 100 may be positioned on the blade 20 uphole (in the context of FIG. 2) of the gauge cutters 25. Protective inserts 100 may be positioned in proximity to the cutting elements of bit 10. For example, protective inserts 100 may be positioned directly adjacent to gauge cutters 25 (as shown in FIG. 2). Protective inserts 100 may be positioned further uphole on blade 20 and attached at gauge diameter 62 (as shown in FIGS. 1A and 1B). For example, protective insert 100 is placed on a surface so that the protective insert 100 can extend beyond the gauge diameter 62 and provide the primary protection for the gauge cutters 25. For instance, protective inserts 100 may be positioned on that section of bit 100 where the face of blade 20 is substantially parallel to casing 50 and substantially perpendicular to the bottom of the borehole, e.g., protective inserts 100 may be positioned at about 90° on the drill bit profile or about 90° to vertical centerline 16 (as shown in FIGS. 1A and 1B).

Referring again to FIG. 2, protective insert 100 may provide a protective function by extending laterally beyond gauge diameter 62 of bit 10 (e.g., beyond the distance of the cutting surfaces of gauge cutters 62) and into drift distance 72 by a selected protective insert extension distance or overgauge distance 82. The protective insert extension distance 82 may be defined as the additional lateral distance that the furthest point of the protective insert 100 from the centerline 16 extends beyond the gauge diameter 62. The operational area of protective insert 100 may be designed to be “overgauge”, e.g., the outermost point of protective insert 100 may be within drift distance 72. The protective insert extension distance 82 may be equal to drift distance 72. The distance the protective insert 100 extends beyond the gauge diameter 62 and into drift distance 72, e.g., extension distance 82, may be selected based on the dimensions of bit 10, casing material, hardness of the rock formation, the material selected for the protective insert 100, among other factors. For example, extension distance 82 may be a range from about 0.005″ to about 0.050″, depending on gauge diameter 62 of bit 10, casing diameter 50, and the desired material of construction of protective insert 100, for example.

Protective insert 100 may be composed of a variety of materials suitable for drilling operations, or the downhole environment. For example, protective inserts 100 may comprise TCI (tungsten carbide) inserts, PDC (polycrystalline diamond compact) inserts, matrix material inserts, diamond impregnated inserts, or any other suitable material. The size and material of protective insert 100 may be selected to provide protection for gauge cutters 25 from the force of impact, and may be selected such that protective insert 100 wears down at a selected rate. For example, protective inserts 100 may be selected to wear down at a higher rate than the superabrasive cutting faces 23 of gauge cutters 25, especially when in direct contact with a virgin rock formation. For instance, during drilling operations after drillout, protective inserts 100 may quickly wear down to gauge diameter 62 and allow the gauge cutters 25 to engage the formation.

Protective insert 100 may be coupled to bit 10 by any method suitable for drilling operations or the downhole environment. For example, protective insert 100 may be brazed or infiltrated into bit 10 e.g., a matrix bit. Bit 10 may comprise apertures sized or threaded to receive protective inserts 100. Protective inserts 100 may be affixed to bit 10 by pressing, pinning or threading protective inserts 100 into these apertures, for example. Protective insert 100 may also be brazed into such apertures. Protective inserts 100 may be removably coupled to bit 10 to allow ease of repair or replacement.

Protective insert 100 may be shaped and sized to selectively contact or engage the inner surface of casing 50, e.g., to absorb impact and quickly ablate. For example, protective insert 100 may comprise a dome or curved formation, such as a half-dome or sphere. Protective insert 100 may be shaped to distribute the force of impact throughout the protective insert 100 rather than the point of contact. Protective insert 100 may act as a bearing surface against casing 50 so as to minimize friction against the wall, thereby preventing gouging. Protective insert 100 may be shaped or selected, e.g., by the selected material or a smooth gradient shape, to minimize rotation disruption of bit 10 after impact. For example, protective insert 100 may comprise shapes with a smooth contact point, such as an elliptical, oval, ovoid, “pill”, or “bullet” shape, for example.

The illustrated embodiments of the active gauge protection may provide a number of advantages. For example, protective inserts 100 protect gauge cutters 25 during the entry, lowering, and drillout of concrete shoe 90 at the bottom of the hole by providing a physical barrier between the gauge cutters and metal casing 50. Protective inserts 100 may act as the first physical contact points between drill bit 10 and metal casing 50 should drill bit 10 wander off-center, through drift distance 72, and into the casing, e.g., bit whirl. Protective inserts 100 may act as the point of contact to absorb the force and prevent movement that would expose the hardened cutters to the casing wall, which may damage or gouge the interior of casing 50.

The illustrated embodiments of protective inserts 100 may also provide the first point of contact if drill bit 10 moves or deviates toward the casing wall. Protective inserts 100 may act as a smooth bearing surface to allow drill bit 10 to continue to rotate while in contact with the casing wall either during drillout of the shoe or traversal down the hole. Protective inserts 100 may comprise curved and smooth surface as well as its material of construction help to both reduce the impact of the bit against the metal wall of the casing and prevent gouging by the harder, more durable cutting elements. Materials of construction can vary to ensure compatibility with the casing wall as well as act as a force-absorbing material. Protective inserts 100 may serve as a guide to assist with centering drill bit 10 as it is positioned into and through casing 50.

The illustrated embodiments of protective inserts 100 may also act as an additional gauge guide once the drill bit penetrates concrete shoe 90 at the bottom of casing 50 and engages the rock formation. During drillout, protective inserts 100 may continue to provide both bit and casing lateral protection and resist abrasion from the shoe material; however, upon entering virgin formation beneath the shoe, the material of construction may quickly wears down to gauge diameter against the rock formation, thereby fully exposing the gauge cutters to the formation. The material and shape for protective inserts 100 can be selected to optimize this effect based on the properties of the target rock formation.

In another example, once the operators set casing 50, a smaller drill bit 10 may be used to drill the next interval. As a result, there is some play between the casing 50 and the next hole size to be drilled. This difference may allow drill bit 10 to bounce around in the casing, which may damage drill bit 10 and the casing. Protective inserts 100 may act to protect both drill bit 10 and casing 50 in this situation. Conventional drill bits do not address this problem because conventional designs, e.g., such as the standards set forth by the American Petroleum Institute (API), typically do not permit components of the drill bit to extend beyond the drill diameter.

From the foregoing detailed description of specific embodiments of the invention, it should be apparent that an apparatus and method for protecting the drill bit and casing that are novel have been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow. 

1. A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, the drill bit comprising: a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter; and a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.
 2. The drill bit of claim 1, wherein the protective insert ablates at a greater rate than the gauge cutter.
 3. The drill bit of claim 2, wherein the protective insert comprises a tungsten carbide insert.
 4. The drill bit of claim 2, wherein the protective insert comprises a matrix material.
 5. The drill bit of claim 2, wherein the protective insert comprises a diamond impregnated insert.
 6. The drill bit of claim 2, wherein the protective insert is operable to ablate to allow the gauge cutter to engage the rock formation.
 7. The drill bit of claim 6, wherein the protective insert ablates from about the overgauge distance to about gauge diameter once the drill bit engages the rock formation.
 8. The drill bit of claim 7, wherein the protective insert is positioned adjacent to the gauge cutter.
 9. The drill bit of claim 8, wherein the protective insert is positioned on the drill bit at about 90 degrees to a vertical centerline of the drill bit.
 10. The drill bit of claim 9, wherein the protective insert comprises a smooth bearing surface operable to allow the drill bit to rotate within the casing.
 11. The drill bit of claim 10, wherein the overgauge distance is about the drift distance.
 12. The drill bit of claim 10, wherein the overgauge distance is less than the drift distance.
 13. The drill bit of claim 12, wherein the overgauge distance is a range from about 0.005″ to about 0.050″.
 14. The drill bit of claim 10, wherein the protective insert comprises a substantially dome shaped surface.
 15. The drill bit of claim 10, wherein the protective insert comprises a substantially elliptical shaped surface.
 16. The drill bit of claim 14, wherein the protective insert is brazed to the drill bit.
 17. A method of protecting a gauge cutter of a drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, comprising the steps of: positioning a protective insert on the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance; positioning the drill bit within the casing; and substantially preventing the gauge cutter from contacting the casing inner wall along a selected length of the casing.
 18. The method of claim 17, further comprising the step of abrading the protective insert to about gauge diameter to allow the gauge cutter to engage the rock formation.
 19. The method of claim 18, further comprising the step of allowing the drill bit to rotate within the casing.
 20. The method of claim 19, further comprising the step of absorbing a portion of the impact of the drill bit contacting the casing inner wall.
 21. The method of claim 19, further comprising the step of centering the drill bit within the casing inner wall for a selected length of the casing. 